U-Pb zircon dates from North American and British Avalonia bracket the Lower–Middle Cambrian boundary interval, with evaluation of the Miaolingian Series as a global unit
Title: U-Pb zircon dates from North American and British Avalonia bracket the Lower–Middle Cambrian boundary interval, with evaluation of the Miaolingian Series as a global unit
Abstract High-precision U-Pb zircon ages on SE Newfoundland tuffs now bracket the Avalonian Lower–Middle Cambrian boundary. Upper Lower Cambrian Brigus Formation tuffs yield depositional ages of 507.91 ± 0.07 Ma (Callavia broeggeriZone) and 507.67 ± 0.08 Ma and 507.21 ± 0.13 Ma (Morocconus-Condylopyge eliAssemblage interval). Lower Middle Cambrian Chamberlain’s Brook Formation tuffs have depositional ages of 506.34 ± 0.21 Ma (Kiskinella cristataZone) and 506.25 ± 0.07 Ma (Eccaparadoxides bennettiZone). The composite unconformity separating the Brigus and Chamberlain’s Brook formations is constrained between these ages. An Avalonian Lower–Middle Cambrian boundary between 507.2 ± 0.1 and 506.3 ± 0.2 Ma is consistent with maximum depositional age constraints from southwest Laurentia, which indicate an age for the base of the Miaolingian Series, as locally interpreted, of ≤ 506.6 ± 0.3 Ma. The Miaolingian Series’ base is interpreted as correlative within ≤ 0.3 ± 0.3 Ma between Cambrian palaeocontinents, although its exact synchrony is questionable due to taxonomic problems with a possibleOryctocephalus indicus-plexus, invariable dysoxic lithofacies control ofO. indicusand diachronous occurrence ofO. indicusin temporally distinct δ13C chemozones in South China and SW Laurentia. The lowest occurrence ofO. indicusassemblages is linked to onlap (epeirogenic or eustatic) of dysoxic facies. A united Avalonia is shown by late Early Cambrian volcanics in SW New Brunswick; Cape Breton Island; SE Newfoundland; and the Wrekin area, England. The new U-Pb ages revise Avalonian geological evolution as they show rapid epeirogenic changes through depositional sequences 4a–6. more »« less
Hodgin, Eben B.; Nelson, Lyle L.; Wall, Corey J.; Barrón-Díaz, Arturo J.; Webb, Lucy C.; Schmitz, Mark D.; Fike, David A.; Hagadorn, James W.; Smith, Emily F.
(, Geology)
null
(Ed.)
Abstract We present chemostratigraphy, biostratigraphy, and geochronology from a succession that spans the Ediacaran-Cambrian boundary in Sonora, Mexico. A sandy hematite-rich dolostone bed, which occurs 20 m above carbonates that record the nadir of the basal Cambrian carbon isotope excursion within the La Ciénega Formation, yielded a maximum depositional age of 539.40 ± 0.23 Ma using U-Pb chemical abrasion–isotope dilution–thermal ionization mass spectrometry on a population of sharply faceted volcanic zircon crystals. This bed, interpreted to contain reworked tuffaceous material, is above the last occurrences of late Ediacaran body fossils and below the first occurrence of the Cambrian trace fossil Treptichnus pedum, and so the age calibrates key markers of the Ediacaran-Cambrian boundary. The temporal coincidence of rift-related flood basalt volcanism in southern Laurentia (>250,000 km3 of basalt), a negative carbon isotope excursion, and biological turnover is consistent with a mechanistic link between the eruption of a large igneous province and end-Ediacaran extinction.
Kuiper, Yvette D; Murray, Daniel P; Crowley, James L
(, Geological Society of America data repository)
Kuiper, Yvette D; Murphy, J Brendan; Nance, R Damian; Strachan, Rob A; Thompson, Margaret D
(Ed.)
The Avalon terrane of southeastern New England is a composite terrane, in which various crustal blocks may have different origins and/or tectonic histories. The northern part (west and north of Boston, Massachusetts) correlates well with Avalonian terranes in Newfoundland, Nova Scotia and New Brunswick, Canada, based on rock types and ages, U–Pb detrital zircon signatures of metasedimentary rocks, and Sm–Nd isotope geochemistry data. In the south, fewer data exist, in part because of poorer rock exposure, and the origins and histories of the rocks are less well constrained. We conducted U–Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) analysis on zircon from seven metasedimentary rock samples from multiple previously interpreted subterranes, in order to constrain their origins. Two samples of Neoproterozoic Plainfield Formation quartzite from the previously interpreted Hope Valley subterrane in the southwestern part of the southeastern New England Avalon terrane and two from the Neoproterozoic Blackstone Group quartzite from the adjacent Esmond-Dedham subterrane to the east have Tonian youngest detrital zircon age populations. One sample of Cambrian North Attleboro Formation quartzite of the Esmond-Dedham subterrane yielded an Ediacaran youngest detrital zircon age population. Detrital zircon populations of all five samples include abundant Mesoproterozoic zircon and smaller Paleoproterozoic and Archean populations, and are similar to those of the northern part of the southeastern New England Avalon terrane and the Avalonian terranes in Canada. These are interpreted as having a Baltican/Amazonian affinity based primarily on published U-Pb and Lu-Hf detrital zircon data. Based on U-Pb detrital zircon data, there is no significant difference between the Hope Valley and Esmond-Dedham subterranes. Detrital zircon of two samples of the Price Neck and Newport Neck formations of the Neoproterozoic Newport Group in southern Rhode Island is characterized by large ~647–643 and ~745–733 Ma age populations and minor zircon up to ~3.1 Ga. This signature is most consistent with a northwest African affinity. The Newport Group may thus represent a subterrane, terrane or other crustal block with a different origin and history than the southeastern New England Avalon terrane to the northwest. The boundary of this Newport Block may be restricted to the boundaries of the Newport Group, or it may extend as far north as Weymouth, MA, as far northwest as (but not including) the North Attleboro Formation quartzite and associated rocks in North Attleboro, MA, and as far west as Warwick, RI, where eastern exposures of the Blackstone Group quartzite exist. The Newport Block may have amalgamated with the Amazonian/Baltican part of the Avalon terrane prior to mid-Paleozoic amalgamation with Laurentia, or have arrived as a separate terrane after accretion of the Avalon terrane. Alternatively, it may have arrived during the formation of Pangea and been stranded after the breakup of Pangea, as has been proposed previously for rocks of the Georges Bank in offshore Massachusetts. If the latter is correct, then the boundary between the Newport Block and the southeastern New England Avalon terrane is the Pangean suture zone.
Farrell, TP; Cothren, HR; Sundberg, FA; Schmitz, MD; Dehler, CM; Landing, E; Karlstrom, KE; Crossey, LJ; Hagadorn, JW
(, Geological Society of America Bulletin)
We present a refined global Furongian (late Cambrian) time scale derived through the application of Bayesian age modeling, using an integrative assemblage of conditioning likelihoods (age constraints) including U-Pb zircon maximum depositional ages in the Steptoean positive isotopic carbon excursion (SPICE) reference section in Smithfield Canyon (Utah, USA) and nearby McPherson Canyon (Idaho, USA); Re-Os geochronology from the SPICE-bearing interval of the Andrarum-3 core (Scania, Sweden); and new high-precision chemical abrasion−isotope dilution−thermal ionization mass spectrometry U-Pb zircon tuff ages from Avalonian Wales. We embed these radioisotopic ages within a novel probabilistic treatment of biozones to establish temporal constraints on rock accumulation rates in the Great Basin (USA), the duration of the SPICE event, and Laurentian trilobite biozones correlated to the global Cambrian time scale. Results reveal a beginning of 494.5 (+0.7/−0.6) Ma and an end of 487.3 ± 0.08 Ma for the Furongian Epoch, representing a reduction of the traditional late Cambrian by ∼30% and an extension of the Ordovician by nearly half a million years. Furthermore, the SPICE is confined to a duration of 2.6 (+0.9/−0.8) m.y. Our new approach to integrating faunal succession into Bayesian age modeling can help to constrain rock accumulation rates and possible hiatuses in sections with limited radioisotopic ages. Additionally, it offers a robust calibration tool for further refining the numerical calibration of the geologic time scale, for testing hypotheses about the rates of trilobite evolution and extinction, for evaluating causes of the SPICE, and for constraining paleoclimatic conditions including atmospheric O2 levels.
Cothren, Hannah R.; Farrell, Thomas P.; Sundberg, Frederick A.; Dehler, Carol M.; Schmitz, Mark D.
(, Geology)
Abstract The Steptoean Positive Isotopic Carbon Excursion (SPICE) is a prominent +4–5‰ shift in the Cambrian δ13C record used for global chronostratigraphic correlation. The onset of this excursion is traditionally placed at the base of the Pterocephaliid trilobite biomere (base of the Furongian Series). Recent studies have documented local controls on the expression of the SPICE and emphasize the need for chronostratigraphic standards for these complex biogeochemical signals. We build upon prior work in western Laurentia by integrating δ13C and biostratigraphy with high-precision isotope dilution U-Pb detrital zircon maximum depositional ages that are coincident with the onset, peak, and falling limb of the SPICE. Our study provides the first useful numerical age constraint for the onset of the SPICE and the Laurentian trilobite biozones and requires revision of the late Cambrian geologic time scale boundaries by several million years.
Busch, James F.; Rooney, Alan D.; Meyer, Edward E.; Town, Caleb F.; Moynihan, David P.; Strauss, Justin V.
(, Canadian Journal of Earth Sciences)
null
(Ed.)
The age and nature of the Neoproterozoic – early Paleozoic rift–drift transition has been interpreted differently along the length of the North American Cordillera. The Ediacaran “upper” group (herein elevated to the Rackla Group) of the Coal Creek inlier, Yukon, Canada, represents a key succession to reconstruct the sedimentation history of northwestern Laurentia across the Precambrian–Cambrian boundary and elucidate the timing of active tectonism during the protracted breakup of the supercontinent Rodinia. These previously undifferentiated late Neoproterozoic – early Paleozoic map units in the Coal Creek inlier are herein formally defined as the Lone, Cliff Creek, Mount Ina, Last Chance, Shade, and Shell Creek formations. New sedimentological and stratigraphic data from these units is used to reconstruct the depositional setting. In the Last Chance Formation, chemostratigraphic observations indicate a ca. 5‰ δ 13 C carb gradient coincident with the globally recognized ca. 574–567 Ma Shuram carbon isotope excursion. Map and stratigraphic relationships in the overlying Shell Creek Formation provide evidence for latest Ediacaran – middle Cambrian tilting and rift-related sedimentation. This provides evidence for active extension through the Cambrian Miaolingian Series in northwestern Canada, supporting arguments for a multiphase and protracted breakup of Rodinia.
Landing, Ed, Schmitz, Mark D, Westrop, Stephen R, and Geyer, Gerd. U-Pb zircon dates from North American and British Avalonia bracket the Lower–Middle Cambrian boundary interval, with evaluation of the Miaolingian Series as a global unit. Retrieved from https://par.nsf.gov/biblio/10558120. Geological Magazine 160.9 Web. doi:10.1017/s0016756823000729.
Landing, Ed, Schmitz, Mark D, Westrop, Stephen R, & Geyer, Gerd. U-Pb zircon dates from North American and British Avalonia bracket the Lower–Middle Cambrian boundary interval, with evaluation of the Miaolingian Series as a global unit. Geological Magazine, 160 (9). Retrieved from https://par.nsf.gov/biblio/10558120. https://doi.org/10.1017/s0016756823000729
Landing, Ed, Schmitz, Mark D, Westrop, Stephen R, and Geyer, Gerd.
"U-Pb zircon dates from North American and British Avalonia bracket the Lower–Middle Cambrian boundary interval, with evaluation of the Miaolingian Series as a global unit". Geological Magazine 160 (9). Country unknown/Code not available: Cambridge University Press. https://doi.org/10.1017/s0016756823000729.https://par.nsf.gov/biblio/10558120.
@article{osti_10558120,
place = {Country unknown/Code not available},
title = {U-Pb zircon dates from North American and British Avalonia bracket the Lower–Middle Cambrian boundary interval, with evaluation of the Miaolingian Series as a global unit},
url = {https://par.nsf.gov/biblio/10558120},
DOI = {10.1017/s0016756823000729},
abstractNote = {Abstract High-precision U-Pb zircon ages on SE Newfoundland tuffs now bracket the Avalonian Lower–Middle Cambrian boundary. Upper Lower Cambrian Brigus Formation tuffs yield depositional ages of 507.91 ± 0.07 Ma (Callavia broeggeriZone) and 507.67 ± 0.08 Ma and 507.21 ± 0.13 Ma (Morocconus-Condylopyge eliAssemblage interval). Lower Middle Cambrian Chamberlain’s Brook Formation tuffs have depositional ages of 506.34 ± 0.21 Ma (Kiskinella cristataZone) and 506.25 ± 0.07 Ma (Eccaparadoxides bennettiZone). The composite unconformity separating the Brigus and Chamberlain’s Brook formations is constrained between these ages. An Avalonian Lower–Middle Cambrian boundary between 507.2 ± 0.1 and 506.3 ± 0.2 Ma is consistent with maximum depositional age constraints from southwest Laurentia, which indicate an age for the base of the Miaolingian Series, as locally interpreted, of ≤ 506.6 ± 0.3 Ma. The Miaolingian Series’ base is interpreted as correlative within ≤ 0.3 ± 0.3 Ma between Cambrian palaeocontinents, although its exact synchrony is questionable due to taxonomic problems with a possibleOryctocephalus indicus-plexus, invariable dysoxic lithofacies control ofO. indicusand diachronous occurrence ofO. indicusin temporally distinct δ13C chemozones in South China and SW Laurentia. The lowest occurrence ofO. indicusassemblages is linked to onlap (epeirogenic or eustatic) of dysoxic facies. A united Avalonia is shown by late Early Cambrian volcanics in SW New Brunswick; Cape Breton Island; SE Newfoundland; and the Wrekin area, England. The new U-Pb ages revise Avalonian geological evolution as they show rapid epeirogenic changes through depositional sequences 4a–6.},
journal = {Geological Magazine},
volume = {160},
number = {9},
publisher = {Cambridge University Press},
author = {Landing, Ed and Schmitz, Mark D and Westrop, Stephen R and Geyer, Gerd},
}
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